Extractor



Oct. 7, 1930. J. o. ROBERTS EXTRACTOB Filed Jan. 24, 1928 ulius QRObeI's alto: MG:

Patented Oct. 7, 1930 JULIUS o. nonnn rs, or nnnronvinnngnnxnnsns j I BMQ T. 1

Application filed January 24, visas; Serial jn g49;1s V if;

This invention relatesto a tool tor extractlng broken screws, threaded pipes and other screw-threaded devices from bores in 5 cannot be removed by the usual means.

' It is an object of the invention to provide a tool of this character which will positively grip the object to be extracted so that, by turning the tool in one direction, the said object willbe unscrewed and thus removed readily. i

A further object is to provide an extracting tool the gripping action of which increases in proporton to the force exerted during the application of the tool to the threaded object to be removed. Y

"With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and 111 the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may-be made within the scope oi: what is claimed, without departing from the spirit of the invention.

In the accompanying drawings the preferred form of the invention has been shown, In said'drawings,

i Figure 1 is an elevationof the tool, the

same being shown in position immediately prior to insertion into a screw about to be withdrawn from a structure in which it has been broken. 1 y Figure 2 is an end view of the tool.

' Referring to the figures by characters of reference 1 designates a shank of any desired shape andfproportions which can be formed with a suitable head 2 at one end 40 although this is not essential. The other end of the shank has a reduced cylindrical exq tension 3 the free end of which isslightly tapered as shown at 4, it being understood that the extent of thistaper may be varied. A screw thread is cut. into the extension 3 as shown at 5 and is intersected by longitudinal' grooves 6 whereby the ends of the" threads thus produced form cutting elements. Usually the extension 3 is tobe formed with a left handthread but where the tool is to beeinployed for relnoviiigan object having a left-hand thread, the thread on the -extension3 will befright hand. which they are seated and from which they 1 Formed lin theshanlr l at that end from a which .the extension .3 projects, are a desired .55 number of notchesor recesses? forming cutting edges 8 which extend radially of the shank and are so designed as to cut in the direction in which the tool is rotated while being applied.

Should it be desired to remove a threaded object which has broken off in a structure the procedure necessary to remove the object would depend on the natureof the object. Should it be a solid screw S which has broken 6 off in a metal: block B or the like, it would first be necessary to drill a recess R in the screw, the diameter of this recess being slightly les than the diameter ofthe extension Said extension would then be placed 0 with its tapered ends in the outer end of the recess and by forcing the tool longitudinally and at the sametime rotating it, it will work intothe recess It, cutting a thread therein which will engage the thread on the extension. Thus the radial cutting or biting edges 8 on the shank lwillbe fed gradually against the exposed end of the screw S and as soon'as this biting action takes placethe screw will become tightly anchored to thetool. This will result in unscrewing the screw during further rotationof the tool in the same direction so that the screw can thus be removed readily.

Should it be desired to remove a broken 5 piece of threaded pipe, it would not be necessary to form the bore. Instead a tool would be used having an extension 3 which will feed properly into the pipe to cause the biting edges 8 toengage and properly grip the end 9 of the pipe. i i

This tool can be cheaply made and will be I found of great utility where it is desired-to remove broken screw-threaded parts from those structures in which they are seated. It is also advantageous because it will not expand the object being removed. What is claimed is:

A tool for extracting an ext riofl y-i threaded object from a threaded b incluc-L ing a shank, an extension at one end thereof having a tapered portion insertable into a bore in the object to be unscrewed, means on the extension for cutting a screw-thread in the wall ofsaid bore pitched oppositely to the exterior thread on the object and for feeding the tool toward said object, and means on the shank for biting into said object at the completion of the thread cutting operation of the extension, thereby to couple the threadcd object to the shank andunscrew saidobject during continued rotation'of the shank in the same direction, the pitch of the thread cutting means being such as to cause the tool to bite into the engaged object Withincreasi'ng" pressure proportioned to the resistance encountered in unscrewing the object.

In testimony that I claim the foregoing as my own, I have hereto afliXed my signature.

JULIUS O. ROBERTS. 

